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chapter 5
The System Unit
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Learning Objectives
After you have read this chapter, you should be able to:
1 Differentiate between the four basic types of system units.
2 Describe system boards, including sockets, slots, and bus lines.
3 Recognize different microprocessors, including microprocessor chips and specialty processors.
4 Compare different types of computer memory, including RAM, ROM, and flash memory.
5 Explain expansion slots and cards.
6 Describe bus lines, bus widths, and expansion buses.
7 Describe ports, including standard and specialized ports.
8 Identify power supplies for desktop, laptop, tablet, and mobile devices.
9 Explain how a computer can represent numbers and encode characters electronically.
Why should I read this chapter?
System units are getting smaller, faster, cheaper, and more powerful. These staggering improvements are resulting in microchips integrating with all aspects of our lives. For example, in the future we will
see everything from microchips embedded in the brain that improve
mental capacity to sensors that can literally read your mind.
This chapter covers the things you need to know to be prepared
for this ever changing digital world, including:
• Types of microcomputers—learn the strengths and weaknesses
of desktops, laptops, tablets, and mobile devices.
• Computer components—understand the impact microprocessors and memory have on the power of a computer.
• Peripherals and upgrades—expand your computer’s abilities and
speed.
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Introduction
“
Hi, I’m Liz, and I’m a computer technician. I’d like
to talk with you about the different types of system
units for personal computers. I’d also like to talk
about various electronic components that make
your computer work.
”
Why are some computers more powerful than others? The answer lies in
three words: speed, capacity, and flexibility. After reading this chapter, you
will be able to judge how fast, powerful, and versatile a particular personal
computer is. As you might expect, this knowledge is valuable if you are
planning to buy a new personal computer system or to upgrade an existing system. (The Computer Buyer’s Guide at the end of this book provides
additional information.) This knowledge will help you evaluate whether or
not an existing system is powerful enough for today’s new and exciting
applications.
Sometime you may get the chance to watch when a technician opens
up a personal computer. You will see that it is basically a collection of electronic circuitry. While there is no need to understand how all these components work, it is important to understand the principles. Armed with this
knowledge, you will be able to confidently make sound purchasing and
upgrading decisions.
To efficiently and effectively use computers, you need to understand the
functionality of the basic components in the system unit, including the system board, microprocessor, memory, expansion slots and cards, bus lines,
ports, cables, and power supply units.
System Unit
ethics
Labor costs are much less in China
than in the United States. As a result,
many computers and peripherals sold
last year were manufactured there.
While this has resulted in the loss of
jobs elsewhere, it has also improved
the standard of living for millions
of Chinese. Unfortunately, working
conditions in Chinese factories have
been widely reported to be well
below acceptable standards. Do you
think consumers have an ethical
responsibility regarding where and/or
how products are manufactured?
To see more ethical issues,
visit our website at www.mhhe.
com/ce2015 and select Student
Edition and then Ethics.
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The system unit, also known as the system chassis, is a container that houses
most of the electronic components that make up a computer system.
At one time all system units were in a separate case. Advances in the miniaturization of electronic components, however, have led to smaller and smaller computers
with system units that share containers with other parts of the computer system.
As we have previously discussed, a personal computer is the most widely used
type of computer. It is the most affordable and designed to be operated directly by
an end user. The four most common types are desktop, laptop, tablet, and mobile
devices. Each has a unique type of system unit.
Desktops
This is the most powerful type of personal computer. Most desktops have their
system unit in a separate case. This case contains the system’s electronic components and selected secondary storage devices. Input and output devices, such as
a mouse, keyboard, and monitor, are located outside the system unit. This type
of system unit is designed to be placed either horizontally or vertically. Desktop
system units that are placed vertically are sometimes referred to as a tower unit or
tower computer. (See Figure 5-1.)
Some desktop computers, like Apple’s iMac, have their monitor and system
unit housed together in the same case. These computers are known as an all-inone. (See Figure 5-2.)
Laptops
Although typically not as powerful as desktops, laptops are portable and much
smaller. Their system units are housed with selected secondary storage devices
and input devices (keyboard and pointing device). Located outside the system
unit, the monitor is attached by hinges. Laptops are often called notebooks.
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Figure 5-1 Tower unit
Figure 5-2 All-in-one
Ultrabooks, also known as ultraportables or mini notebooks, are a type of
very portable laptop. They are lighter and thinner and have a longer battery life
than other laptops. They accomplish these advantages by leaving out components
such as optical drives and using energy-efficient microprocessors. (See Figure 5-3.)
Tablets
Tablets, also known as tablet computers, are the newest and one of the most popular types of computer. They are effectively a thin slab that is almost all monitor
with the system unit located behind the monitor.
Tablets are smaller, lighter, and generally less powerful than laptop computers.
Like a laptop, tablets have a flat screen but typically do not have a standard keyboard. Instead, most tablets use a virtual keyboard that appears on the screen and
is touch-sensitive.
Mini tablets are a type of tablet with a smaller screen. While mini tablets operate like a traditional tablet, they typically do not have all the functionality of the
bigger tablets. Their most significant advantage is that they are easier to transport
in pockets and purses. (See Figure 5-4.)
Figure 5-3 Ultrabook
Figure 5-4 Mini tablet
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Mobile Devices
Mobile devices, also known as handheld computers, are the smallest and are
designed to comfortably fit into the palm of one hand. These systems contain an
entire computer system, including the electronic components, secondary storage,
and input and output devices. These devices are smaller and generally less powerful than tablets.
By far the most popular mobile device is the smartphone. It greatly extends the
capabilities of a cell phone by providing computing power. In addition to capturing and sending audio and video, smartphones run apps, connect to the Internet,
and more. Their system unit is located behind the display screen.
Components
Personal computers come in a variety of different sizes, shapes, and capabilities.
While they look different and each has its own unique features, they share surprisingly similar components, including system boards, microprocessors, and memory. (See Figure 5-5.)
Desktop
Tablet
Laptop
Smartphone
Figure 5-5 System unit components
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Bus lines
Socket
Slot
Figure 5-6 System board
concept check
What is the system unit?
Describe and compare the four most common types of personal computers.
What are tower units? What is an all-in-one? What is an ultrabook? What is a mini tablet?
System Board
The system board is also known as the mainboard or motherboard. The system
board controls communications for the entire computer system. All devices and
components connect to the system board, including external devices like keyboards and monitors and internal components like hard disk drives and microprocessors. The system board acts as a data path and traffic monitor, allowing the
various components to communicate efficiently with one another.
On a desktop computer, the system board is typically located at the bottom
of the system unit or along one side. It is a large flat circuit board covered with a
variety of different electronic components including sockets, slots, and bus lines.
(See Figure 5-6.)
• Sockets provide a connection point for small specialized electronic parts called
chips. Chips consist of tiny circuit boards etched onto squares of sandlike material
called silicon. These circuit boards can be smaller than the tip of your finger. (See
Figure 5-7.) A chip is also called a silicon chip, semiconductor, or integrated circuit.
Chips typically are mounted onto chip carriers. (See Figure 5-8.) These carriers plug
either directly into sockets on the system board or onto cards that are then plugged
into slots on the system board. Sockets are used to connect the system board to a
variety of different types of chips, including microprocessor and memory chips.
Figure 5-7 Chip
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environment
Have you ever wondered what
you should do with your old
computers, monitors, and
mobile devices? The last thing
you want to do is throw them
away. First, consider donating
them to various charitable
organizations that work with
local schools and low-income
families. Otherwise, recycle
them. Many computer retailers
near you accept used devices
and components for recycling,
even if they are broken.
Alternatively, visit the website
of your local government to find
the electronics recycling center
nearest you.
To see more environmental facts,
visit our website at www.mhhe/
ce2015.com and select Student
Edition and then Environment.
Figure 5-8 Chip mounted onto a chip carrier
• Slots provide a connection point for specialized cards or circuit boards. These
cards provide expansion capability for a computer system. For example, a
wireless networking card plugs into a slot on the system board to provide a
connection to a local area network.
• Connecting lines called bus lines provide pathways that support communication among the various electronic components that are either located on the
system board or attached to the system board.
Generally, the system board found on a desktop is larger than that found on a
laptop, and much larger than one found on a tablet or a mobile device. Although
these system boards vary in size, they nevertheless all perform the same function
of communicating between the components of the personal computer.
concept check
What is the system board, and what does it do?
Define and describe sockets, slots, and bus lines.
What are chips? How are chips attached to the system board?
Microprocessor
In most personal computer systems, the central processing unit (CPU) or
processor is contained on a single chip called the microprocessor. The microprocessor is the “brains” of the computer system. It has two basic components: the
control unit and the arithmetic-logic unit.
• Control unit: The control unit tells the rest of the computer system how to
carry out a program’s instructions. It directs the movement of electronic signals between memory, which temporarily holds data, instructions, and processed information, and the arithmetic-logic unit. It also directs these control
signals between the CPU and input and output devices.
• Arithmetic-logic unit: The arithmetic-logic unit, usually called the ALU, performs two types of operations: arithmetic and logical. Arithmetic operations
are the fundamental math operations: addition, subtraction, multiplication,
and division. Logical operations consist of comparisons such as whether one
item is equal to (5), less than (<), or greater than (>) the other.
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Microprocessor Chips
Chip processing capacities are often expressed in word sizes. A word is the number of bits (such as 16, 32, or 64) that can be accessed at one time by the CPU. The
more bits in a word, the more data a computer can process at one time. Eight bits
group together to form a byte. A 32-bit-word computer can access 4 bytes at a
time. A 64-bit-word computer can access 8 bytes at a time. Therefore, the computer
designed to process 64-bit words has greater processing capacity. Other factors
affect a computer’s processing capability including how fast it can process data
and instructions.
The processing speed of a microprocessor is typically represented by its
clock speed, which is related to the number of times the CPU can fetch and
process data or instructions in a second. Older microcomputers typically process data and instructions in millionths of a second, or microseconds. Newer
microcomputers are much faster and process data and instructions in billionths of a second, or nanoseconds. Supercomputers, by contrast, operate
at speeds measured in picoseconds—1,000 times as fast as microcomputers.
(See Figure 5-9.) Logically, the higher a microprocessor’s clock speed, the faster
Unit
Speed
the microprocessor. However, some processors can handle multiple instrucMicrosecond Millionth of a second
tions per cycle or tick of the clock; this means that clock speed comparisons
can only be made between processors that work the same way.
Nanosecond
Billionth of a second
At one time, personal computers were limited by microprocessors that could
Picosecond
Trillionth of a second
support a single CPU that controlled operations. These computers were limited to processing one program at a time. Now, many personal computers have
Figure 5-9 Processing speeds
multicore processors that can provide two or more separate and independent
CPUs. For example, a quad-core processor could have one core computing a complex Excel spreadsheet, a second core creating a report using Word, a third core
locating a record using Access, and a fourth core running a multimedia presentaProcessor
Manufacturer
tion all at the same time. More significantly, however, is the potential for personal
A-Series
AMD
computers to run very large, complex programs that previously required expensive and specialized hardware.
E-Series
AMD
For multicore processors to be used effectively, computers must understand
Atom
Intel
how to divide tasks into parts that can be distributed across each core—an operai7
Intel
tion called parallel processing. Operating systems such as Windows 8 and Mac OS
X support parallel processing. Software developers use this technology for a wide
Figure 5-10 Popular microprocessors
range of applications from scientific programs to sophisticated computer games.
See Figure 5-10 for a table of popular microprocessors.
Specialty Processors
In addition to microprocessor chips, a variety of more specialized processing chips
have been developed.
• Coprocessors are specialty chips designed to improve specific computing
operations. One of the most widely used is the graphics coprocessor, also
called a GPU (graphics processing unit). These processors are designed
to handle a variety of specialized tasks such as displaying 3-D images and
encrypting data.
• Many cars have more than 70 separate specialty processors to control nearly
everything from fuel efficiency to satellite entertainment and tracking systems.
concept check
Name and describe the two components of a microprocessor.
Define word, clock speed, multicore chip, and parallel processing.
privacy
Did you know that one type of
specialty processor is devoted
exclusively to protecting your
privacy? Called cryptoprocessors,
these microchips perform
encoding and decoding of data
faster and more securely than
a CPU. These specialized chips
exist in ATMs, TV set-top boxes,
and smartcards.
To see more privacy facts, visit
our website at www.mhhe.
com/ce2015 and select Student
Edition and then Privacy.
What are specialty processors? Describe coprocessors.
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Chip
Circuit board
Memory
Memory is a holding area for data, instructions, and
information. Like microprocessors, memory is contained on chips connected to the system board. There
are three well-known types of memory chips: randomaccess memory (RAM), read-only memory (ROM), and
flash memory.
RAM
Random-access memory (RAM) chips hold the program (sequence of instructions) and data that the CPU is
presently processing. (See Figure 5-11.) RAM is called temporary or volatile storage because everything in most types of RAM is lost as soon as the computer is
turned off. It is also lost if there is a power failure or other disruption of the electric current going to the computer. Secondary storage, which we shall describe in
Chapter 7, does not lose its contents. It is permanent or nonvolatile storage, such
as the data stored on a hard disk. For this reason, as we mentioned earlier, it is a
good idea to frequently save your work in progress to a secondary storage device.
That is, if you are working on a document or a spreadsheet, every few minutes
you should save, or store, the material.
Cache (pronounced “cash”) memory improves processing by acting as a temporary high-speed holding area between the memory and the CPU. The computer
detects which information in RAM is most frequently used and then copies that
information into the cache. When needed, the CPU can quickly access the information from the cache.
Having enough RAM is important! For example, to use the standard version of
Microsoft Office 2013, you need 2 GB, or 2 billion bytes, of RAM. Some applications, such as photo editing software, may require even more. Fortunately, additional RAM can be added to a computer system by inserting an expansion module
called a DIMM (dual in-line memory module) into the system board. The capacity or amount of RAM is expressed in bytes. There are three commonly used units
of measurement to describe memory capacity. (See Figure 5-12.)
Other types of RAM include DRAM, SDRAM, DDR, and direct RDRAM. To
learn more about these other types of RAM, visit our website at www.mhhe.com/
ce2015 and select Student Edition, then Explore, and then RAM.
Even if your computer does not have enough RAM to hold a program, it might
be able to run the program using virtual memory. Most of today’s operating systems support virtual memory. With virtual memory, large programs are divided
into parts and the parts are stored on a secondary device, usually a hard disk. Each
part is then read into RAM only when needed. In this way, computer systems are
able to run very large programs. To learn more about how virtual memory works,
visit our website at www.mhhe.com/ce2015 and select Student Edition, then
Explore, and then Memory.
Figure 5-11 RAM chips mounted on circuit board
Unit
Capacity
Megabyte (MB)
1 million bytes
Gigabyte (GB)
1 billion bytes
Terabyte (TB)
1 trillion bytes
Figure 5-12 Memory capacity
ROM
Read-only memory (ROM) chips have information stored in them by the manufacturer. Unlike RAM chips, ROM chips are not volatile and cannot be changed
by the user. “Read only” means that the CPU can read, or retrieve, data and programs written on the ROM chip. However, the computer cannot write—encode or
change—the information or instructions in ROM.
Not long ago, ROM chips were typically used to contain almost all the instructions for basic computer operations. For example, ROM instructions are needed
to start a computer, to access memory, and to handle keyboard input. Recently,
however, flash memory chips have replaced ROM chips for many applications.
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Flash Memory
Flash memory offers a combination of the features of RAM and ROM. Like RAM,
it can be updated to store new information. Like ROM, it does not lose that information when power to the computer system is turned off.
Flash memory is used for a wide range of applications. For example, it is used to
store the start-up instructions for a computer. This information is called the system’s
BIOS (basic input/output system). This information would include the speType
Use
cifics concerning the amount of RAM and the type of keyboard, mouse, and
RAM
Programs and data
secondary storage devices connected to the system unit. If changes are made
ROM
Fixed start-up instructions
to the computer system, these changes are reflected in flash memory. To learn
more about how a computer starts up and BIOS, visit our website at www.
Flash
Flexible start-up instructions
mhhe.com/ce2015 and select Student Edition, then Explore, and then Boot.
See Figure 5-13 for a summary of the three types of memory.
Figure 5-13 Memory
concept check
What is memory? Name and describe three types.
What are cache memory, DIMM, and virtual memory?
Define ROM and flash memory.
Expansion Slots and Cards
As previously mentioned, many personal computers allow users to expand their
systems by providing expansion slots on the system board. Users can insert
optional devices known as expansion cards into these slots.
(See Figure 5-14.) Ports on the cards allow cables to be connected from the expansion cards to devices outside the system unit. (See Figure 5-15.) There are a wide range of different
types of expansion cards. Some of the most commonly used
expansion cards are:
• Graphics cards provide high-quality 3-D graphics and animation for games and simulations.
• Sound cards accept audio input from a microphone and
convert it into a form that can be processed by the computer. Also, these cards convert internal electronic signals
to audio signals so they can be heard from external speakers or home theater systems.
• Network interface cards (NIC), also known as network
adapter cards, are used to connect a computer to a network. (See Figure 5-16.) The network allows connected
computers to share data, programs, and hardware. The
network adapter card typically connects the system unit
to a cable that connects to the network.
• Wireless network cards allow computers to be connected without cables. As
we will discuss in Chapter 9, wireless networks in the home are widely used to
share a common Internet connection. Each device on the network is equipped
with a wireless network card that communicates with the other devices.
Slot
Figure 5-14 Expansion cards fit into
slots on the system board
Plug and Play was originally a set of specific hardware and software standards developed by Intel, Microsoft, and others. As hardware and software have
evolved, however, Plug and Play has become a generic term that is associated with
the ability to plug any device such as a printer or monitor into a computer and
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Ports
Figure 5-15 Expansion card with three ports
Figure 5-16 Network interface card
have it play or work immediately. Some devices, however,
are not Plug and Play and require that new device drivers be
installed, as discussed in Chapter 4.
To meet the size constraints of laptop computers, tablets,
and mobile devices, small credit card–sized expansion cards
known as PC cards have been developed. These cards plug
into PCMCIA slots (called PC card slots) or, most recently,
ExpressCard slots. (See Figure 5-17.)
Figure 5-17 PC card
concept check
What are expansion slots and cards? Name four expansion cards.
Discuss Plug and Play.
What are PC cards, PCMCIA slots, and ExpressCard slots?
Bus Lines
As mentioned earlier, a bus line—also known simply as a bus—connects the parts
of the CPU to each other. Buses also link the CPU to various other components on
the system board. (See Figure 5-18.) A bus is a pathway for bits representing data
and instructions. The number of bits that can travel simultaneously down a bus is
known as the bus width.
A bus is similar to a multilane highway that moves bits rather than cars from
one location to another. The number of traffic lanes determines the bus width. A
highway (bus line) with more traffic lanes (bus width) can move traffic (data and
instructions) more efficiently. For example, a 64-bit bus can move twice as much
information at a time as a 32-bit bus. Why should you even care about what a bus
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line is? Because as microprocessor chips have changed, so have bus lines.
Bus design or bus architecture is an important factor relating to the speed
and power for a particular computer. Additionally, many devices, such as
expansion cards, will work with only one type of bus.
Every computer system has two basic categories of buses. One category,
called system buses, connects the CPU to memory on the system board. The
other category, called expansion buses, connects the CPU to other components on the system board, including expansion slots.
Expansion Buses
Computer systems typically have a combination of different types of expansion buses. The principal types are USB, FireWire, and PCIe.
• Universal serial bus (USB) is widely used today. External USB devices
are connected from one to another or to a common point or hub and then
onto the USB bus. The USB bus then connects to the PCI bus on the system board. The current USB standard is USB 3.0.
• FireWire buses are similar to USB buses but more specialized. They are
used primarily to connect audio and video equipment to the system board.
• PCI Express (PCIe) is widely used in many of today’s most powerful computers.
Unlike most other buses that share a single bus line or path with several devices,
the PCIe bus provides a single dedicated path for each connected device.
Figure 5-18 Bus is a pathway for bits
concept check
What is a bus, and what is bus width?
What is the difference between a system and an expansion bus?
Discuss three types of expansion buses.
Ports
A port is a socket for external devices to connect to the system unit. (See
Figure 5-19.) Some ports connect directly to the system board, while others connect to cards that are inserted into slots on the system board. Some ports are standard features of most computer systems, and others are more specialized.
Standard Ports
Most desktop and laptop computers come with a standard set of ports for connecting a monitor, keyboard, and other peripheral devices. The most common
ports include
• VGA (Video Graphics Adapter) and DVI (Digital Video Interface) ports provide connections to analog and digital monitors, respectively. DVI has become
the most commonly used standard, but VGA ports are still provided on almost
all systems for compatibility with older/lower-cost monitors.
• Universal serial bus (USB) ports can be used to connect several devices to the
system unit and are widely used to connect keyboards, mice, printers, storage
devices, and a variety of specialty devices. One such device, a USB TV tuner
card, allows users to view and record television programs. To learn how you
can use a TV tuner card, see Making IT Work for You: TV Tuners on page 1250.
A single USB port can be used to connect many USB devices to the system unit.
• FireWire ports provide high-speed connections to specialized FireWire devices
such as camcorders and storage devices.
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• Ethernet ports are a
high-speed networking
port that has become
a standard for many
of today’s computers.
Ethernet allows you to
connect multiple computers for sharing files,
or to a DSL or cable
modem for high-speed
Internet access.
Ethernet
FireWire
Specialized Ports
USB
In addition to standard
ports, there are numerous
specialty ports including eSATA, HDMI, MIDI,
MiniDP, and Thunderbolt.
DVI
Figure 5-19 Ports
HDMI
VGA
• External Serial
Advanced Technology
Attachment (eSATA)
ports provide highspeed connections
for external hard disk
drives, optical discs,
and other large secondary storage devices.
• High Definition Multimedia Interface (HDMI) ports provide high-definition
video and audio, making it possible to use a computer as a video jukebox or
an HD video recorder.
• Musical instrument digital interface (MIDI) ports are a special type of port
for connecting musical instruments like an electronic keyboard to a sound
card. The sound card converts the music into a series of digital instructions.
These instructions can be processed immediately to reproduce the music or
saved to a file for later processing.
• Mini DisplayPort (MiniDP or mDP) ports are an audiovisual port typically used to connect large monitors. These ports are used with many Apple
Macintosh computers.
• Thunderbolt ports, first introduced in
Apple’s MacBook Pro computer, provide
high-speed connections. A single port can
connect up to seven separate devices connected one to another. Thunderbolt ports
promise to replace a number of different types
of ports including Mini DisplayPorts.
Cables
USB
DVI
Figure 5-20 Cables
124
FireWire
Ethernet
Cables are used to connect exterior devices to the
system unit via the ports. One end of the cable is
attached to the device, and the other end has a
connector that is attached to a matching connector
on the port. (See Figure 5-20.)
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Making
IT work for you
TV TUNERS
Do you already use a DVR (digital video recorder) in order to record your favorite TV shows? Although many cable and satellite
companies offer this device, did you know that Windows Media Center can perform the same function? All you need is a device
called a TV tuner that connects your antenna or cable to your computer. Below are the steps to turn your Windows-based computer into a DVR.
Installing a TV Tuner A TV tuner is essentially a piece of hardware that allows your computer to process and display a cable or
TV signal. Although some (usually pricey) PCs may include this technology, it is usually necessary to purchase it separately.
The easiest ones to install are those that connect externally to a USB port, such as the AverTV Hybrid Volar Max.
1
2
• Plug the TV tuner into an available USB port on your computer.
• Connect a coaxial cable directly from your cable outlet or over-the-air
antenna to the back of the TV tuner. If Windows does not automatically
install the tuner, consult the user manual for instructions.
3
4
• Start Windows Media Center.
• With your TV tuner installed, it will guide you through a setup process,
including a long scan for all available channels from your cable or antenna.
Using Windows Media Center This utility is included with Windows 7 and can be purchased as an upgrade for Windows 8.
Although it contains many tools to manage your music, photos, and movies, we focus on its DVR capabilities for TV and cable.
1
2
• Once setup is complete, click the TV option from the main menu.
• Click Guide, and scroll up/down and
left/right until you find a show you
wish to record.
3
• Right-click the show, and choose
Record from the menu.
4
• To play back a recorded show, choose
Recorded TV from the TV menu, and
click the show you wish to play back.
5
• Once you have watched a recording,
choose the Delete option to free up
space on your hard drive. The number
of hours you can record is limited by
your available hard drive space.
If you have a high-speed wireless network and several PCs in your home, you will have the capability to watch your
recorded shows via Media Center’s streaming ability. The web is continually changing, and some of the specifics presented in
this Making IT Work for You may have changed.
To learn about other ways to make information technology work for you, visit our website at www.mhhe.com/ce2015 and select Student
Edition and then Making IT Work.
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Power Supply
tips
Does your laptop seem to be losing its charge sooner than it used to?
These batteries do lose power over time; however, you can take some
steps to slow down the aging process.
1 Balance adapter and battery use. The best practice is to use the laptop on battery
●
power for a little while without draining it completely (50 percent charge, for example),
followed by charging it back to 100 percent. Modern batteries should not be drained to
0 percent each day.
Computers require direct current
(DC) to power their electronic components and to represent data and
instructions. DC power can be provided indirectly by converting alternating current (AC) from standard
wall outlets or directly from batteries.
2 Calibrate it. Your laptop’s manufacturer will recommend that you calibrate, or reset, your
●
battery every few months. Follow its guidelines on the web or in your instruction manual,
• Desktop computers have a power
supply unit located within the
system unit. (See Figure 5-21.) This
as it will ensure that the battery meter in your operating system is accurate and that you
unit plugs into a standard wall
are getting the expected charge time.
outlet, converts AC to DC, and
3 Avoid excessive heat. High temperatures can accelerate the deterioration of modern
provides the power to drive all of
batteries. Therefore, avoid exposure to excessive heat and consider purchasing a laptop
the system unit components.
cooler or fan.
• Laptops and tablets use AC
4 Proper storage. If you are not going to use your laptop for a few weeks, most
adapters that are typically located
manufacturers recommend that you remove the battery.
outside the system unit. (See
To see other tips, visit our website at www.mhhe.com/ce2015 and select Student Edition
Figure 5-22.) AC adapters plug
and then Tips.
into a standard wall outlet, convert
AC to DC, provide power to drive
the system unit components, and can recharge the batteries. These computers
can be operated either using an AC adapter plugged into a wall outlet or using
battery power. Their batteries typically provide sufficient power for up to
eight hours before they need to be recharged.
• Like laptops and tablets, mobile devices use AC adapters located outside
the system unit. Unlike laptops and tablets, however, ultrabooks and mobile
devices typically operate only using battery power. The AC adapter is used to
recharge the batteries.
●
●
concept check
What are ports? What do they do?
Describe four standard ports and five specialized ports.
What is a power supply unit? What is an AC adapter?
Figure 5-21 Power supply unit
126
Figure 5-22 AC adapter
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Electronic Data and Instructions
Have you ever wondered why it is said that we live in a digital world? It’s because
computers cannot recognize information the same way you and I can. People follow instructions and process data using letters, numbers, and special characters.
For example, if we wanted someone to add the numbers 3 and 5 together and
record the answer, we might say “please add 3 and 5.” The system unit, however,
is electronic circuitry and cannot directly process such a request.
Our voices create analog, or continuous, signals that vary to represent different tones, pitches, and volume. Computers, however, can recognize only digital
electronic signals. Before any processing can occur within the system unit, a conversion must occur from what we understand to what the system unit can electronically process.
Numeric Representation
What is the most fundamental statement you can make about electricity? It is simply this: It can be either on or off. Indeed, there are many forms of technology that
can make use of this two-state on/off, yes/no, present/absent arrangement. For
instance, a light switch may be on or off, or an electric circuit open or closed. A
specific location on a tape or disk may have a positive charge or a negative charge.
This is the reason, then, that a two-state or binary system is used to represent data
and instructions.
The decimal system that we are all familiar with has 10 digits (0, 1, 2, 3, 4, 5, 6,
7, 8, 9). The binary system, however, consists of only two digits—0 and 1. Each 0
or 1 is called a bit—short for binary digit. In the system unit, the 1 can be represented by a negative charge and the 0 by no electric charge. In order to represent
numbers, letters, and special characters, bits are combined into groups of eight
called bytes. Whenever you enter a number into a computer system, that number
must be converted into a binary number before it can be processed. To learn more
about binary systems and binary arithmetic, visit our website at www.mhhe.com/
ce2015 and select Student Edition, then Explore, and then Binary.
Decimal
Any number can be expressed as a binary number. Binary num00
bers, however, are difficult for humans to work with because they
require so many digits. Instead, binary numbers are often represented
01
in a format more readable by humans. The hexadecimal system, or
02
hex, uses 16 digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F) to represent
03
binary numbers. Each hex digit represents four binary digits, and two
hex digits are commonly used together to represent 1 byte (8 binary
04
digits). (See Figure 5-23.) You may have already seen hex when select05
ing a color in a website design or drawing application, or when enter06
ing the password for access to a wireless network.
Character Encoding
As we’ve seen, computers must represent all numbers with the binary
system internally. What about text? How can a computer provide representations of the nonnumeric characters we use to communicate,
such as the sentence you are reading now? The answer is character
encoding schemes or standards.
Character encoding standards assign a unique sequence of bits
to each character. Historically, personal computers used the ASCII
(American Standard Code for Information Interchange) to represent
characters, while mainframe computers used EBCDIC (Extended
Binary Coded Decimal Interchange Code). These schemes were
quite effective; however, they are limited. ASCII, for example, only
uses 7 bits to represent each character, which means that only 128 total
characters could be represented. This was fine for most characters in
Binary
Hex
00000000
00
00000001
01
00000010
02
00000011
03
00000100
04
00000101
05
00000110
06
07
00000111
07
08
00001000
08
09
00001001
09
10
00001010
0A
11
00001011
0B
12
00001100
0C
13
00001101
0D
14
00001110
0E
15
00001111
0F
Figure 5-23 Numeric
representations
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the English language but was not large enough to support other languages such
as Chinese and Japanese. These languages have too many characters to be represented by the 7-bit ASCII code.
The explosion of the Internet and subsequent globalization of computing have
led to a new character encoding called Unicode, which uses 16 bits. The Unicode
standard is the most widely used character encoding standard and is recognized
by virtually every computer system. The first 128 characters are assigned the same
sequence of bits as ASCII to maintain compatibility with older ASCII-formatted
information. However, Unicode uses a variable number of bits to represent each
character, which allows non-English characters and special characters to be
represented.
concept check
What is the difference between an analog and a digital signal?
What are decimal and binary systems? How are they different?
Compare EBCDIC, ASCII, and Unicode.
Careers in IT
“
Now that you know about system units, I’d like to tell
you about my career as a computer technician.
128
”
Computer technicians repair and install computer components and
systems. They may work on everything from personal computers
and mainframe servers to printers. Some computer technicians are
responsible for setting up and maintaining computer networks.
Experienced computer technicians may work with computer engineers to diagnose problems and run routine maintenance on complex systems. Job growth is expected in this field as computer
equipment becomes more complicated and technology expands.
Employers look for those with certification in computer repair or
associate degrees from professional schools. Computer technicians
also can expect to continue their education to keep up with technological changes. Good communication skills are important in this
field.
Computer technicians can expect to earn an annual salary in the
range of $31,000 to $46,000. Opportunities for advancement typically
come in the form of work on more advanced computer systems.
Some computer technicians move into customer service positions
or go into sales. To learn more about other careers in information
technology, visit us at www.mhhe.com/ce2015 and select Student
Edition and then Careers.
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A LOOK TO THE FUTURE
Chips inside Your Brain
Have you ever thought it would be possible to be able to communicate with a computer . . . by merely thinking? Researchers
are working with various devices (usually worn on the head) that
can use your basic thoughts to move objects, such as wheelchairs. However, the future will lie in implanted microchips that
can communicate directly with our nerve cells. Although their
initial purpose will be to treat a variety of medical conditions,
they could eventually (and controversially) be used to improve
various brain functions of otherwise healthy individuals.
For over a decade, doctors have been able to use
deep brain stimulation (DBS)
to treat several disorders such
as Parkinson’s disease. As
successful as it has been for
many patients, those implants
simply send preset electrical
impulses to the brain. They do
not involve an active communication between nerve cells
and machines. Researchers
working on a chip known as
ReNaChip hope to change
this by using a programmable
computer chip that is responsive to what is going on in the
patient’s brain. This silicon chip
can measure the brain’s electrical activity and then deliver
the appropriate stimulation
when and where it is needed.
Another brain implant that is currently being developed aims
to help the blind regain some sight. A microchip is implanted
in the brain’s visual cortex, which is responsible for processing
images. This chip would communicate wirelessly with a camera
located inside special eyeglasses worn by the individual. The
images captured by that camera would be processed by the
chip and then fed directly to the nerves in this area of the brain.
Getting close to the world of the unbelievable, researchers are improving on the ability of computers to actually read
human thoughts. Currently, one research team has been able
to use a chip implant and computer to read the thoughts of
a stroke victim in order to allow her to move a robotic hand.
Although the success rate is not 100 percent and the processing is limited to basic movements, the patient has already been
able to get the robotic arm to
hold a cup of coffee by thinking about it. This research will
hopefully lead to improved,
thought-controlled prosthetic
devices for millions of disabled
individuals.
Many ethicists are concerned by the potential use of
such chips to improve human
abilities instead of treating
medical conditions. For example, with tiny chips being able
to store so much, people could
use brain implants to improve
their memory. This can lead to
a variety of scenarios where
the individual with the implants
could have an unfair advantage over those who don’t
have them. However, others
disagree, arguing that the integration of technology and biology is to be expected, and it
is nothing more than the next
step in human evolution.
If such a technology became widespread and affordable,
would you opt to receive a chip implant? Would you make a
distinction between using one for a medical condition and simply for improving your mental abilities? Do you think the future of
humanity lies in the merging of technology with human biology?
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VISUAL SUMMARY
The System Unit
SYSTEM UNIT
System unit (system chassis) contains electronic components. The most common personal computers are
desktop, laptop, tablet, and mobile device.
Desktop
Desktop system units located in separate case; tower
unit (tower computer) has vertical system unit; all-inone computer combines system unit and monitor.
Laptop
Laptop (notebook) system units contain secondary
storage devices and input devices. Ultrabooks (ultraportables, mini notebooks) are lighter, thinner, and
have longer battery life than other laptops.
SYSTEM BOARD
The system board (mainboard or motherboard) controls all communication for the computer system. All
external and internal devices and components connect to it.
• Sockets provide connection points for chips
(silicon chips, semiconductors, integrated circuits).
Chips are mounted on chip carriers.
• Slots provide connection points for specialized
cards or circuit boards.
• Bus lines provide pathways to support
communication.
Tablet
Tablet system units are located behind the monitor.
They are smaller, lighter, and generally less powerful
than laptops and use a virtual keyboard. Mini tablets
are smaller version of a traditional tablet.
Mobile Devices
Mobile devices (handheld computers) fit comfortably
in one hand. Smartphones are most popular type.
System unit is located behind the display screen.
Components
Each type of system unit has the same basic components including system board, microprocessor, and
memory.
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To efficiently and effectively use computers, you need to understand the functionality of the basic components
in the system unit: system board, microprocessor, memory, expansion slots and cards, bus lines, ports, and
cables. Additionally, you need to understand how data and programs are represented electronically.
MICROPROCESSOR
EXPANSION SLOTS AND CARDS
In most personal computers, the central processing
unit (CPU) or processor is contained on a single chip
called the microprocessor. It has two basic components: a control unit and ALU.
Microprocessor Chips
A word is the number of bits that can be accessed by
the microprocessor at one time. Clock speed represents the number of times the CPU can fetch and process data or instructions in a second.
Multicore processors can provide multiple independent CPUs. Parallel processing requires programs
that allow multiple processors to work together to run
large complex programs.
Specialty Processors
Specialty processors include graphics coprocessors,
also known as GPU or graphics processing unit (processes graphic images), and processors in automobiles (monitor fuel efficiency, satellite entertainment,
and tracking systems).
MEMORY
Memory holds data, instructions, and information.
There are three types of memory chips.
RAM
RAM (random-access memory) chips are called temporary or volatile storage because their contents are
lost if power is disrupted.
• Cache memory is a high-speed holding area for
frequently used data and information.
• DIMM (dual in-line memory module) is used to
expand memory.
• Virtual memory divides large programs into parts
that are read into RAM as needed.
ROM
ROM (read-only memory) chips are nonvolatile storage and control essential system operations.
Flash Memory
Flash memory does not lose its contents when power
is removed.
Most computers allow users to expand their systems
by providing expansion slots on their system boards
to accept expansion cards.
Examples of expansion cards include graphics
cards, sound cards, network interface cards (NIC; network adapter cards), and wireless network cards.
Plug and Play is the ability for a computer to
recognize and configure a device without human
interaction.
PC cards plug into PCMCIA slots, and ExpressCard
slots accept credit card–sized expansion cards.
BUS LINES
Bus lines, also known as buses, provide data pathways
that connect various system components. Bus width
is the number of bits that can travel simultaneously.
System buses connect CPU and memory. Expansion
buses connect CPU and slots.
Expansion Buses
Three principal expansion bus types are
• USB (universal serial bus) can connect from one
USB device to another or to a common point (hub)
and then onto the system board.
• FireWire bus is similar to USB bus but more
specialized.
• PCI Express (PCIe) bus is widely used; provides a
single dedicated path for each connected device.
THE SYSTEM UNIT
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PORTS
POWER SUPPLY
Power supply units convert AC to DC and power
desktops. AC adapters power laptops and tablets and
recharge batteries.
Ports are connecting sockets on the outside of the system unit.
Standard Ports
Four standard ports are
• VGA (Video Graphics Adapter) and DVI (Digital
Video Interface)—provide connections to
monitors.
• USB (universal serial bus)—widely used to connect keyboards, mice, printers, and storage
devices; one port can connect several devices to
system unit.
• FireWire—provides high-speed connections to
FireWire devices such as camcorders and storage
devices.
• Ethernet—high-speed networking port that has
become a standard for many of today’s computers.
Specialized Ports
Five specialty ports are eSATA (external Serial
Advanced Technology Attachment) for high-speed
connections to large secondary storage devices,
HDMI (High Definition Multimedia Interface) for
high-definition digital audio and video, MIDI for digital music, Mini DisplayPort (MiniDP, mDP) for large
monitors, and Thunderbolt for high-speed connections to up to seven separate devices connected one
to another.
Cables
ELECTRONIC REPRESENTATION
Human voices create analog (continuous) signals;
computers only recognize digital electronic signals.
Numeric Representation
Data and instructions can be represented electronically with a two-state or binary system of numbers
(0 and 1). Each 0 or 1 is called a bit. A byte consists of
8 bits. Hexadecimal system (hex) uses 16 digits to represent binary numbers.
Character Encoding
Character encoding standards assign unique
sequences of bits to each character. Three standards
are
• ASCII—American Standard Code for Information
Interchange. Historically used for personal
computers.
• EBCDIC—Extended Binary Coded Decimal
Interchange Code. Historically used for mainframe
computers.
• Unicode—16-bit code, most widely used standard.
CAREERS IN IT
Computer technicians repair and install computer
components and systems. Certification in computer
repair or associate degree from professional schools
is required. Salary range is $31,000 to $46,000.
Cables are used to connect external devices to the
system unit via ports.
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KEY TERMS
AC adapter (126)
all-in-one (114)
analog (127)
arithmetic-logic unit
(ALU) (118)
arithmetic
operation (118)
ASCII (127)
binary system (127)
BIOS (basic input/output
system) (121)
bit (127)
bus (122)
bus line (118, 122)
bus width (122)
byte (127)
cable (124)
cache memory (120)
central processing unit
(CPU) (118)
character encoding
standards (127)
chip (117)
chip carriers (117)
clock speed (119)
computer
technician (128)
control unit (118)
coprocessor (119)
desktop (114)
digital (127)
DIMM (120)
DVI (Digital Video
Interface) port (123)
EBCDIC (127)
Ethernet port (123)
expansion bus (123)
expansion card (121)
expansion slot (121)
ExpressCard (122)
external Serial Advanced
Technology Attachment
(eSATA) (124)
FireWire bus (123)
FireWire port (123)
flash memory (121)
GPU (119)
graphics card (121)
graphics
coprocessor (119)
handheld
computer (116)
hexadecimal system
(hex) (127)
High Definition
Multimedia Interface
(HDMI) (124)
integrated circuit (117)
laptop (114)
logical operation (118)
mainboard (117)
memory (120)
microprocessor (118)
Mini DisplayPort (MiniDP,
mDP) (124)
mini notebook (115)
mini tablets (115)
mobile device (116)
motherboard (117)
multicore
processor (119)
musical instrument digital
interface (MIDI) (124)
network adapter
card (121)
network interface card
(NIC) (121)
notebook (115)
parallel processing (119)
PC card (122)
PC card slot (122)
PCI Express (PCIe) (123)
PCMCIA slot (122)
personal computer (114)
Plug and Play (121)
port (123)
power supply unit (126)
processor (118)
random-access memory
(RAM) (120)
read-only memory
(ROM) (120)
semiconductor (117)
silicon chip (117)
slot (118)
smartphone (116)
socket (117)
sound card (121)
system board (117)
system bus (123)
system chassis (114)
system unit (114)
tablet (115)
tablet computer (115)
Thunderbolt (124)
tower computer (114)
tower unit (114)
ultrabooks (115)
ultraportables (115)
Unicode (128)
universal serial bus
(USB) (123)
universal serial bus (USB)
port (123)
VGA (Video Graphics
Adapter) port (123)
virtual memory (120)
wireless network
card (121)
word (119)
To test your knowledge of these key terms with animated flash cards, visit our website
at www.mhhe.com/ce2015, select Student Edition, and choose Chapter 5 and then
Flashcards.
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MULTIPLE CHOICE
Circle the correct answer.
1. This container houses most of the electrical components for a computer system.
a. chip carrier
c. system unit
b. system board
d. Unicode
2. The most popular mobile device.
a. all-in-one
c. smartphone
b. handheld
d. ultrabook
3. The mainboard or motherboard is also known as the:
a. computer
c. mobile system
b. board processor
d. system board
4. How many bytes can a 32-bit-word computer access at one time?
a. 1
c. 8
b. 4
d. 16
5. In a personal computer system, the central processing unit is typically contained on
a single:
a. bus
c. module
b. chip
d. RAM
6. This type of memory divides large programs into parts and stores the parts on a secondary storage device.
a. direct
c. random access
b. expanded
d. virtual
7. Also known as NIC, this adapter card is used to connect a computer to a(n):
a. AIA
c. graphics
b. expansion
d. network
8. This provides a pathway to connect parts of the CPU to each other.
a. bus
c. wired
b. Plug and Play
d. wireless
9. The specialized port that connects musical instruments like an electronic keyboard
to a sound card.
a. eSATA
c. MIDI
b. HDMI
d. Thunderbolt
10. Computers can only recognize this type of electronic signal.
a. analog
c. digital
b. bus
d. maximum
For an interactive multiple-choice practice test, visit our website at www.mhhe.com/
ce2015, select Student Edition, and choose Chapter 5 and then Multiple Choice.
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MATCHING
Match each numbered item with the most closely related lettered item. Write your
answers in the spaces provided.
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
cache
flash
multicore
Plug and Play
port
random access
slots
sockets
system
USB
___ 1. A type of multiprocessor chip that provides two or
more separate and independent CPUs.
___ 2. A type of memory that is volatile or loses its
contents when power is turned off.
___ 3. System board component that provides a connection point for specialized cards or circuit boards.
___ 4. Provide connection points for chips.
___ 5. A type of memory that improves processing by
acting as a temporary high-speed holding area
between the memory and the CPU.
___ 6. A type of memory that provides a combination of
features of RAM and ROM.
___ 7. A generic term that is associated with the ability to
attach any device onto a computer and have it play
or work immediately.
___ 8. This bus connects the CPU to memory on the
system board.
___ 9. This port can be used to connect many USB
devices to the system.
___10. A socket for external devices to connect to the
system unit.
For an interactive matching practice test, visit our website at www.mhhe.com/ce2015,
select Student Edition, and choose Chapter 5 and then Matching.
OPEN-ENDED
On a separate sheet of paper, respond to each question or statement.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Describe the four most common types of personal computers.
Describe system boards including sockets, chips, chip carriers, slots, and bus lines.
Discuss microprocessor components, chips, and specialty processors.
Define computer memory including RAM, ROM, and flash memory.
Define expansion slots, cards, Plug and Play, PC cards, PCMCIA slots, and
ExpressCard slots.
Describe bus lines, bus width, system bus, and expansion bus.
Define ports including standard and specialized ports. Give examples of each.
Describe power supply including power supply units and AC adapters.
Discuss electronic data and instructions.
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DISCUSSION
Respond to each of the following questions.
1
Making IT Work for You: TV TUNERS
Did you know that you can record your favorite TV shows with a computer? Review the Making IT
Work for You: TV Tuners on page 125, and then respond to the following: (a) Do you currently have a
DVR in your home? If so, who is the manufacturer? If not, have you considered purchasing one? Why or why not? (b) How do
the Windows Media Center DVR capabilities compare with the DVR offered by your
cable or satellite company? Use a search
engine to help you find these differences.
(c) Find at least two USB-based TV tuners
using any online store. Note their prices
and specifications. What are their main
differences?
2
Privacy: CRYPTOPROCESSORS
Did you know that some systems have
speciality processors that automatically
encrypt data before storing? Review the
Privacy box on page 119, and respond to
the following: (a) Who do you think would
need a cryptoprocessor? Be specific. (b)
Do think these processors would be worthwhile for you to protect your privacy? Why
or why not? (c) Are there any reasons why
you might not want all your data encrypted?
Explain. (d) Do you think that all computer
systems should be required to have cryptoprocessors? Defend your position.
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3
Ethics: JOB LOSS AND WORKING CONDITIONS
Many computer-related products are produced in China, where working conditions are reported
to be well below acceptable standards. Review the Ethics box on page 114, and then respond to
the following: (a) What do you think about products produced in other countries like China? What
are the advantages and disadvantages to consumers? Be specific. (b) What are the ethical issues?
Be specific, and defend your list of issues.
(c) Would you be willing to pay more for a
computer produced entirely in the United
States? More specifically, would you be
willing to pay three times as much for a
smartphone? Why or why not? (d) Do you
think consumers have an ethical responsibility to know how goods are produced?
More specifically, would your purchase
decisions be affected by knowledge about
the working conditions of those who make
the product? Why or why not?
4
Environment: RECYCLING COMPUTER HARDWARE
Have you ever wondered what you should do with your old computers, monitors, and mobile
devices? Review the Environment box on page 118, and then respond to the following: (a) What do
you typically do with your used or broken
computers and mobile devices? (b) What
are three alternatives to throwing these
devices in the trash? (c) Using a search
engine, find one nonprofit organization
near you that will accept used computers.
List the name and URL. (d) Visit the waste
management or recycling page of your
local government’s website. If it does not
have a website, contact it. What is its recommended procedure for discarding your
computers and other electronic devices?
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